1. Field of the Invention
The present invention relates generally to an apparatus and a method for relaying packets on an IP network, and more particularly to a packet relay apparatus and method providing a control of communication paths within the network depending on the types of applications.
2. Description of the Related Arts
In the conventional internet protocol network (hereinafter referred to as “IP network”) such as Internet or intranets, there intermingle various communications including client applications, business applications, file transfer, mails and voices, so that grading of communication qualities on a communication by communication basis, called QOS (quality of service) poses a problem. The grading of the communication quality is performed for example such that a highest communication priority is imparted to the client applications so that a certain voice band is constantly assured, with the communications for the file transfer and mails being suppressed to such a degree as not to impede the other communications. It is problematic in this case how to realize the demands for the thus graded communication qualities. The quality of service QOS is especially essential in a relatively low-speed network such as a wide area network (hereinafter referred to as WAN) whose bands are apt to become full, rather than in a high-speed network such as a local area network (hereinafter referred to as LAN). Two approaches lie to the quality of service QOS, one being how to realize the quality of service demanded, the other being how to separately use a plurality of different communication paths provided. For the separate use of the plurality of communication paths, a packet relay apparatus, typically called, e.g., a layer 4 switch (L4 switch) is provided that uses different packet destinations depending on the applications. When judging the application as a result of analysis of the contents of a packet, this packet relay apparatus sends the packet to the next packet relay apparatus corresponding to the application.
FIG. 1 is an explanatory diagram of a communication form using the packet relay apparatus using different packet destinations depending on the applications. A LAN 101-1 includes a node 100-1 and is followed by a packet relay apparatus 102-1 that uses different packet destinations depending on the applications. In this case, the packet relay apparatus 102-1 is connected via routers 104-1 and 104-2 to an IP network 108 such as WAN or Internet. A LAN 101-2 includes a node 100-2 and is followed by a packet relay apparatus 102-2 that uses different packet destinations depending on the applications. In this case, the packet relay apparatus is connected via routers 106-1 and 106-2 to the IPnetwork 108. In case of the business application, the packet relay apparatuses 102-1 and 102-2 designate the routers 104-1 and 106-1 so that the packet is passed through a communication path 110-1. For the other applications, the packet relay apparatuses 102-1 and 102-2 designate the routers 104-2 and 106-2 so that the packet is passed through a communication path 110-2.
However, in the event of provision of the packet relay apparatuses on a LAN by LAN basis as in FIG. 1, when communications are made between n LANs 100-1 to 100-n by way of the IP network 108 as shown in FIG. 2, a corresponding number of packet relay apparatuses 102-1 to 102-n to the number of LANs are required, resulting in a steep rise of the system costs. Thus, the inventors of this application have conceived that as shown in FIG. 3 the packet relay apparatus 102-1 is disposed only on the LAN to which belongs a specific node 100-1 executing the application, with 1: (n−1) communications between the node 100-1 and the other nodes 100-2 to 100-n using different packet destinations depending on the applications.
FIG. 4 illustrates in an exclusive manner the communication form of the nodes 100-1 and 100-2 of FIG. 3. This is a communication form without the packet relay apparatus 102-2 on one hand of FIG. 16. The node 100-1 sets the packet relay apparatus 102-1 as the default gateway, whereas the node 100-2 sets the router 106-2 as the default gateway. The packet relay apparatus 102-1 is designed so as to send only a business application packet to the router 104-2. If the node 100-1 issues a business application packet at that time, then the packet relay apparatus 102-1 sends the packet to the router 104-2 in compliance with the design, the packet arriving at the node 100-2 by way of the communication path 110-2. However, when the node 100-2 returns the business application packet, it delivers the packet to the router 106-1 that is a default gateway, the packet arriving at the node 100-1 by way of the communication path 110-1. In other words, the send packet belonging to the node 100-1 business application is delivered via the communication path 110-2 to the node 100-2, whereas the reply packet belong to the business application from the node 100-2 is returned via the other communication path 110-1 to the node 100-1. For this reason, separate use is impossible that the business application is exclusively passed through the communication path 110-2, with the other application being passed through the communication path 110-2.